1. Field of the Invention
The present invention relates to storage area networks, and more particularly to virtualization of ports, devices and logic units of such storage area network.
2. Description of the Related Art
As computer network operations have expanded over the years, storage requirements have become very high. It is desirable to have a large number of users access common storage elements to minimize the cost of obtaining sufficient storage elements to hold the required data. However, this has been difficult to do because of the configuration of the particular storage devices. Originally storage devices were directly connected to the relevant host computer. Thus, it was required to provide enough storage connected to each host as would be needed by the particular applications running on that host. This would often result in a requirement of buying significantly more storage than immediately required based on potential growth plans for the particular host. However, if those plans did not go forward, significant amounts of storage connected to that particular host would go unused, therefore wasting the money utilized to purchase such attached storage. Additionally, it was very expensive, difficult and time consuming to transfer unused data storage to a computer in need of additional storage, so the money remained effectively wasted.
In an attempt to solve this problem storage area networks (SANs) were developed. In a SAN the storage devices are not locally attached to the particular hosts but are connected to a host or series of hosts through a switched fabric, where each particular host can access each particular storage device. In this manner multiple hosts could share particular storage devices so that storage space could be more readily allocated between the particular applications on the hosts. While this was a great improvement over locally attached storage, the problem does develop in that a particular storage unit can be underutilized or fills up due to misallocations or because of limitations of the particular storage units. So the problem was reduced, but not eliminated.
To further address this problem and allow administrators to freely add and substitute storage as desired for the particular network environment, there has been a great push to virtualizing the storage subsystem, even on a SAN. In a virtualized environment the hosts will just see very virtual large disks of the appropriate size needed, the size generally being very flexible according to the particular host needs. A virtualization management device allocates the particular needs of each host among a series of storage units attached to the SAN. Elements somewhere in the network would convert the virtual requests into physical requests to the proper storage unit.
Another problem that has occurred in SANs is the inability to move logical unit numbers (LUNs) around inside a storage unit. While virtualization may help hide particular volumes and the physical linkages from the hosts, the virtualization system still will direct activity to a particular port and LUN. However, if there are particular problems, as in a failure of a particular unit, it would be desirable to move the particular LUN to a different location. Alternatively, it would be desirable to be able to move LUNs and ports to load balance the system to allow better overall throughput. However, existing units do not allow this flexibility because a particular LUN is tied to a particular physical port and therefore cannot be readily moved. Thus there currently are problems if a physical unit fails or if the system is not properly load balanced.